Recently, the number of bits of an imaging element (image sensor) is increased and an image comes to be in a dynamic range. Generally, a dynamic range of an image can be expressed by a ratio between minimum luminance and peak luminance. In an HDR image, a contrast ratio between a color with a maximum color value and a color with a minimum color value is, for example, 10000:1 or higher. Thus, the HDR image can express an actual world realistically. The HDR image can record luminance in a whole visible range and can support a dynamic range and a color gamut which are equivalent to those of a visual characteristic of a human. The HDR image has an advantage that shading can be expressed realistically, exposure can be simulated, and brightness can be expressed.
As described above, while an HDR image is photographed on a content production side, displays with various kinds of performance such as a display corresponding to a standard dynamic range (SDR) which is compressed into about one fortieth of the dynamic range and a display, peak luminance of which is 500 nits or 1000 nits and which corresponds to an HDR, are used in houses in which content is viewed. Thus, processing to adapt a dynamic range of original content to performance of a display in an image output destination (hereinafter, also referred to as “display mapping”) is necessary (see, for example, Patent Literature 1).
However, in the display mapping, when conversion of a dynamic range is performed simply by linear scaling, it is concerned that a great amount of information is lost and a visual effect, which is seen by a human, of an image becomes greatly different before and after the conversion. Such a loss of information is not intended by a content producer.